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From the inner specular visible inside his right glove I assume that "primary visibility" is turned on in the objects shape node. But please check anyway
Also make sure the object is not in a display layer that's set to invisible
Further more check if it has any weird things disabled or enabled like Template or the likes.
Best you create a new object and compare all settings with the invisible one and see what's different. (shape and transform nodes! 🙂 )
Select mesh, open shapenode, chose Arnold in list and push Primary Visibility